U. K. business investment slowed and posted no growth in the second quarter of 2017, new data showed, in a sign that uncertainty linked to Brexit negotiations and June's general election may have weighed on firms' long-term plans.

Capital spending by businesses was unchanged compared with the preceding quarter, as well as the corresponding quarter of 2016, standing at GBP43.8 billion ($56.1 billion), the Office for National Statistics said Thursday.

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This appears to be in line with recent anecdotal evidence and surveys that suggest companies are postponing investment as they wait for the fog of political uncertainty to clear.

An electoral setback for Prime Minister Theresa May in June added uncertainty to Britain's path out of the European Union just as negotiations began over its exit terms.

Ministers have suggested the U.K. will seek a transition agreement to give businesses time to adapt, but mixed signals on the shape of such a deal have kept companies on edge.

The second-quarter data came after previous figures showed business investment grew only moderately in the first three months of 2017, expanding by 0.6% on the quarter. This followed a fourth-quarter decline of 0.9%.

Across 2016--the year of the Brexit referendum and significant political upheaval--business investment shrank compared with the previous year for the first time since 2009.

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On Thursday, the ONS confirmed the preliminary second-quarter growth estimate, saying the economy expanded by 0.3% on the quarter, a slight improvement on the 0.2% seen in the first three months of 2017, but still less than half the pace of growth seen in the final quarter of 2016.

The second-quarter figures were in line with the expectations of economists polled by The Wall Street Journal. On an annualized basis, the economy grew by 1.2%, the ONS confirmed.

The second-quarter expansion was driven largely by household expenditure, as well as government spending, each contributing 0.1 percentage points to growth.

Economists say that businesses--particularly exporters--will need to take the growth baton from consumers squeezed by rising prices, if the U.K. economy is to avoid stuttering as Brexit talks get under way.

There was little sign of that rebalancing in the second quarter, with both business investment and net trade making no contribution to economic growth.

Inflation stood at 2.6% in July, down from May's peak of 2.9%, but still significantly above the Bank of England's 2.0% target.

Write to Wiktor Szary at Wiktor.Szary@wsj.com and Jason Douglas at jason.douglas@wsj.com